This invention relates to control systems for gas powered vehicles, and more particularly to a control system for improving fuel consumption in a conventional automobile or similar vehicle.
The present crisis regarding the cost and supply of gasoline for automotive use has resulted in a widespread effort to decrease fuel consumption. Along with this major problem is the further need to reduce noxious emissions to a low level and to control pollution.
Although much progress has been made, the problems still persist and efforts to find solutions continue. This disclosure contributes to the solution of some of these problems by changing the driver-engine-transmission interface to prevent the waste of fuel that occurs with state-of-the-art practice. While most readily applicable to the design of new vehicles, the system disclosed can be retrofitted to many of the approximately fifty million fuel-inefficient vehicles with large engines to significantly reduce both their fuel consumption and their exhaust emissions during the years they will continue in use.
For example, it is apparent that considerable energy is wasted in automobiles which employ direct accelerator pedal control of the throttle. In such vehicles, the engine rotates at relatively high speeds when engine torque is not required to propel the vehicle. In most instances when a driver desires to slow down due to road conditions or otherwise, he normally does not fully release the accelerator pedal and merely reduces the displacement of the pedal slightly to control the speed. This driving practice consumes substantially more fuel than would a complete release of the pedal attendant with a full throttle closure.
To circumvent the above problem, the control system to be described includes a pedal control which operates to control the speed of the vehicle, rather than the speed of the engine. If the pedal controls the vehicle speed directly, driver control is not necessary when more or less engine torque is required. If the driver wishes to slow down, only a slight change in the pedal position is required to result in the throttle being fully closed. If, for example, the car is going down hill and engine torque is not required to maintain the speed, the driver does not have to move his foot as the throttle will close and stay closed until the bottom of the hill or whenever torque is again required to maintain the speed constant. With this system of accelerator pedal control, the throttle is substantially closed when engine torque is not required without driver action, thus resulting in a substantial improvement in fuel economy.
The control system includes an accelerator pedal design in which the pedal is automatically caused to selectively control either vehicle speed or the engine speed. The engine speed mode is used in a transient way to supplement the vehicle speed mode in order to improve the shifting of transmission gears and the engagement of direct drive when engine braking is required. In addition, the engine speed mode is useful when the car is stationary, in neutral, or in reverse, although substantially reducing the gain of the servo control in the vehicle speed mode provides an alternative design.
The control system further improves fuel efficiency by utilizing the engine closer to its maximum power capacity (and therefore substantially more efficiently) for a greater percentage of the driving time, particularly at cruising speeds. This is accomplished by automatically causing the vehicle to accelerate cyclically for short controlled intervals so as to load the engine more fully to improve its fuel efficiency, while maintaining the average speed relatively constant. The periods of acceleration are followed by periods of coasting so that the fuel consumption during these coasting intervals is very low. The intervals between pulses of acceleration automatically are caused to increase when the drag or resistance to coasting is low, and automatically to decrease when the drag is high. When the coasting intervals are very small, as in hill climbing, the pulsing is automatically deactivated.
The control system may further employ coasting or free wheeling operation for further achieving fuel economy. Free wheeling, direct drive, and clutch controlled direct drive mechanisms suffer from the problem that there is frequently an objectionable shock transient when these devices are engaged. The control system to be described includes means for automatically momentarily bringing the engine shaft to the proper speed just prior to engagement with the drive shaft to thus compensate for the above problem.
It is therefore a primary object of the present invention to provide an improved automobile control system capable of achieving significant reductions in fuel consumption.